Methods for the transfer of image deposits formed by electroscopic marking particles or toners of the liquid dispersed or dry type from the surface of a photoconductive or dielectric recording member to a receiving member surface are well known. Such methods may involve the use of corona generating means as is well known in electrophotographic office copying equipment and the like. Alternatively roller transfer methods may be used in which the toned recording member is contacted with the receiving member surface in the nip of a pair of rollers or in the nip formed between a roller and a flat plate. One roller or the flat plate of the nip pair is preferably conductive and grounded, whereas the second roller may have at least a relatively conducting surface which acts as a current limiting device when a transfer voltage is applied thereto. Such roller transfer methods are described for example in U.S. Pat. No. 3,862,848.
In the prior art methods previously referred to either the photoconductive or dielectric recording member or the receiving member comprises a paper web. Consequently in those instances in which so called liquid dispersed toners are used to image the recording member surface, the paper web allows movement of excess dispersant liquid away from the interface between the recording member and receiving member surfaces in such a manner that the electroscopic marking particles are not dislodged. However in those instances in which it is required to transfer an image deposit from a smooth and impervious recording member surface to a smooth and impervious receiving member surface, the prior art methods hereinbefore disclosed are not applicable as the image deposits are only held to the recording member surface by electrostatic forces associated with the electrostatic latent image and the flow or movement of surplus dispersant between the two members causes toner particles to be displaced laterally.
The present invention teaches a method whereby such disadvantages of prior art transfer methods in relation to transfer of image deposits from one smooth impervious surface to another may be overcome.